Stabilized halogen-containing resins

ABSTRACT

MIXTURES OF SULFUR-CONTAINING ORGANO-TIN COMPOUNDS AND ORGANO-TIN MALEATES AS STABILIZERS FOR HALOGEN-CONTAINING RESINS.

United States Patent Oihce 3,655,616 Patented Apr. 11, 1972 3,655,616 STABILIZED HALOGEN-CONTAINING RESINS James T. Freeze, Huntington, N.Y., and Alan L. Fikes, Dublin, Califi, assignors to Pfizer Inc., New York, NY. No Drawing. Continuation of application Ser. No. 598,942, Dec. 5, 1966, which is a continuation-in-part of application Ser. No. 398,065, Sept. 21, 1964. This application Oct. 20, 1970, Ser. No. 82,519

Int. Cl. C081? 45/62 US. Cl. 260-45.75 K 2 Claims ABSTRACT OF THE DISCLOSURE Mixtures of sulfur-containing organo-tin compounds and organo-tin maleates as stabilizers for halogen-containing resins.

This application is a continuation of application Ser. No. 598,942 filed Dec. 5, 1966 and now abandoned and said latter application was a continuation -part of application Ser. No. 398,065 filed Sept. 21, 1964 and now abandoned.

This invention relates to stabilized plastic compositions. More particularly, it is concerned with heat and light resistant halogen-containing resins containing, as stabilizers, ongano-tin derivatives of sulfur compounds and of maleic acid and its esters.

It is a matter of common knowledge and experience that heat and light, individually and collectively, have a harmful effect on halogen-containing resins. For example, polymers of vinyl chloride and copolymers of vinyl chloride with other polymerizable monomers show a strong tendency to darken and lose their desirable physical properties when exposed to light or to heat. These effects have limited the usefulness of such resins, especially Where it has been necessary to heat the materials to compound them with other ingredients on a plastics mill, for example, or where it is the usual practice to expose articles fabricated from such resins to light.

The instability of these resins has been overcome in the art by adding to them certain chemical materials, known as stabilizers. Especially noteworthy and efficient resin stabilizers are organo metallic compounds derived from tin. Special mention is made of two classes of organo-tin compounds which have been found to impart exceptional stability to halogen-containing resins against the deteriorative eifects of heat and light: sulfurcontaining organo-tin stabilizers such as organo-tin mercaptides, organo-tin mercapto esters, organo-tin mercapto alcohols, andthe like; and organo-tin maleate stabilizers.

While these two classes of organo-tin stabilizers have been employed separately in the heat and light stable compositions developed in the art, it has now been found that using them together, in the same plastic composition, within the precise limitations to be described hereinafter, provides a truly remarkable synergistic effect. Thus, it is observed that the stability of halogen-containing resins is so improved by adding these mixtures of stabilizers that for the first time there are obtained plastic compositions with properties more useful than those stabilized with equal amounts of the organo-tin compounds individually. This discovery also provides economic advantages to resin compounders, who may now select stabilizers from each class, combining them on the basis of lowest ultimate cost and still obtain heat and light stability adequate for the fabricated end-use contemplated for the plastic.

It is, accordingly, a principal object of the instant invention to provide improved plastic compositions.

It is a further object of the instant invention to provide plastic compositions with improved resistance to heat and light.

It is a still further object of the instant invention to provide stabilized halogen-containing resin compositions more economically than heretofore.

These and other objects readily apparent to those skilled in the art reside in the novel compositions of the instant invention which are, in essence: Plastic compositions stabilized against heat and light, including as an essential constituent a halogen-containing resin, a sulfur containing stabilizer selected from the group consisting of organo-tin mercaptides, organo-tin mercapto esters and organo-tin mercapto alcohols, and for each part by weight of said stabilizer from about 1 to about 4 parts by weight of an organo-tin maleate stabilizer.

The halogen-containing resins contemplated by the instant invention include those containing a plurality of vinyl chloride units such as polymers of vinyl chloride and conjoint polymers of vinyl chloride with another polymerizable compound, for example, copolymers of vinyl chloride with esters of acrylic and methacrylic acids, and with acrylonitrile; copolymers of vinyl chloride with vinyl esters of aliphatic acids, particularly vinyl acetate; copolymers of vinyl chloride with diene compounds and unsaturated dicarboxylic acids or their anhydrides, such as copolymers of vinyl chloride with diethyl maleate, diethyl fumarate or maleic anhydride; after-chlorinated polymers and copolymers of vinyl chloride; copolymers of vinyl chloride and vinylidene chloride with unsaturated aldehydes, ketones and others, such as acrolein, crotonaldehyde, methyl vinyl ketone, methyl vinyl ether, isobutyl vinyl ether, and the like; polymers of vinylidene chloride and copolymers of the same with vinyl chloride and other polymerizable compounds; polymers of vinyl chloroacetate and dichlordivinyl ether; chlorinated polymers of vinyl acetate; chlorinated polymeric esters of acrylic and alpha-substituted acrylic acids; polymers of chlorinated styrenes, for example, dichlorostyrene; chlorinated rubber; chlorinated polymers of ethylene; polymers and after-chlorinated polymers of chlorobutadienes, and their copolymers with vinyl chloride; rubber hydrochloride and chlorinated rubber hydrochloride; and mixtures of the polymers recited herein with each other or other polymerizable compounds. The corresponding bromides and fluorides lend themselves equally well to the preparation of the valuable new plastic compositions.

Special mention is made of a particularly efiective embodiment of the instant invention; these are plastics compositions wherein the said sulfur-containing stabilizer is a compound of the formula wherein R and R are monovalent hydrocarbon radicals and 3X, and SX are radicals of a mercapto compound selected from the group consisting of aliphatic mercaptans having up to 18 carbon atoms, aromatic mercaptans, monohydric and polyhydric mercaptoalcohols and mercaptoalcohol esters, mercapto acids and mercapto acid esters. R and R may be aliphatic, aromatic, or alicyclic groups, such as methyl, ethyl propyl, butyl, amyl, hexyl, octyl, lauryl, allyl, benzyl, phenyl, tolyl, cyclohexyl, and the like.

Suitable sources for the radicals SX and 5X are aliphatic and aromatic mercaptans having from up to 18 carbon atoms, for example, butyl, decyl and dodecyl mercaptan, thionaphthol, thiobenzyl alcohol, phenoxyethyl, mercaptan, and the like. Radicals SX and SX can also be derived from mercapto alcohols, such as mono thioethylene glycol, mono thiopropylene glycol, thioglycerol, thiodiethylene, glycol, and esters of the mercaptoethanols such as thioglycol 2-ethyl hexoic acid esters, and the like. Furthermore, radicals SX and 8X can be derived from the esters of mono and dibasic aliphatic and aromatic acids, such as thioglycolic acid esters and esters of beta thiopropionic acid, thiolactic acid, thiobutyric acid, alpha mercapto lauric acid, thiomalic acid, thiosalicylic acid, and the like. Especially useful as sulfur-containing stabilizers are dialkyl tin bis-thiozbenzoates, dialkyl tin bis-2-ethylhexylthioglycolate and dialkyl tin bis-laurylmercaptide. These compounds are readily available commercially in some instances and all can be made by techniques familiar to those skilled in the art. In this connection, reference is made to Smith, Organotin Stabilizers, Tin Research Institute, Middlesex, England, 1959, especially pp. -20, which provides reference to procedures for preparing the aforesaid organo-tin compounds, and to Mack et al., US. 2,914,506.

The instant invention also contemplates, in One of its embodiments, plastic compositions of the aforementioned type in which the said organo-tin maleate stabilizer is a compound selected from the group consisting of those of the formulas wherein n is a finite integer equal to at least 1, R and R are defined as hereinabove and R is a monovalent hydrocarbon radical.

The maleates with the first mentioned formula are polymeric in structure, being derived generally from dialkyl tin starting materials and maleic acid or anhydride. Especially convenient in the instantly contemplated compositions is dibutyl tin maleate, since it is readily available commercially. The maleates with the second mentioned formula are generically dialkyl tin esters of maleic acid half esters. The maleic acid half esters are derived from alcohols containing from 1 to 18 carbon atoms, such as methanol, ethanol, propanol, hexanol, octanol, 2-ethylhexanol, dodecanol, hexadecanol, octadecanol, and the like. Among the illustrative maleates can be mentioned dibutyl tin bis-(mono-Z-ethylhexyl maleate) and dibutyl tin bis (mono-lauryl maleate). These stabilizers are readily available commercially or can be prepared by methods familiar to those skilled in the art. In this connection, illustrative teachings can be found in Quattlebaum, US. 2,307,157 and in reference cited in Smith, op. cit. pages 3-5, inc.

The stabilized plastic compositions of the instant invention may be prepared by incorporating the stabilizer mixtures into vinyl resins, which may contain plasticizers, fillers, pigments, dyes, ultraviolet absorbing agents, densifying agents, and other additives in addition to the resins, by admixing in an appropriate mill or mixer or by any of the well known methods which provide for uniform distribution through the plastic compositions.

The stabilizer mixtures may be advantageously employed in concentrations of as little as about 0.01% by weight of the resin or as much as about 10%. Ordinarily, however, concentrations of from about 0.01% to 5% are preferred for reasons of economy, greater concentrations providing relatively little additional benefit.

In addition, to the novel stabilized plastic compositions set forth hereinabove, the instant invention also contemplates novel stabilizing mixtures comprising a sulfur-containing organo-tin compound and from 1 to 4 parts by weight of an organo-tin maleate based on the weight of said compoundr of compounds of the formulae R o o 0 H n is a finite integer equal to at least one;

X and X are each selected from the group consisting of COR aryl, alkaryl and aralkyl of from about 6 to 9 carbon atoms; alkyl and alkenyl bearing up to 3 substituents each selected from the group consisting of hydroxy, alkyloxy, alkylthio, carboxy and carbalkyloxy, each of said alkyl and alkenyl groups containing up to about 18 carbon atoms;

And R, R R and R are each selected from the group consisting of alkyl and alkenyl of up to about 18 carbon atoms, and aryl, alkaryl and aralkyl of from about 6 to 9 carbon atoms. Particularly elfective as stabilizers are embodiments wherein R and R are butyl and X and X are phenylcarbonyl, carbo-Z-ethylhexyloxy-methyl, and dodecyl, respectively, and wherein R and R are butyl and R is 2-ethylhexyl.

The following examples are illustrative of the novel compositions of this invention. They are intended to be illustrative only, and are not to be construed as limiting in any manner whatsoever.

EXAMPLE I Plastic compositions are made with the following ingredients in parts by weight:

Composition A B C D Polyvinyl chloride 100 100 100 Stabilizer:

Dibutyl tin bis-Iaurlymercaptid Dibutyl tin maleate Lubricant, stearic acid The ingredients are mixed together, then compounded on a plastics mill for 4 minutes at 171 C. The hot batches are sheeted off at a thickness of about 0.050 inch and samples of the sheeted stocks are heated at C. in a circulating air oven. The color of the sample's is observed when they are taken off the mill and at 15 minute intervals in the oven:

Composition: Observation A Amber off the mill; black at 15 minutes. B White off the mill; light yellow at 15 Thus, it is seen that the composition D, which is within the scope of the instant invention, exhibits enhanced heat stability when compared with compositions stabilized with the maleate alone (C) and with the sulfur-containing stabilizer alone (B). Especially noteworthy is the observation that even after 60 minutes at these high temperatures composition D remains white, while the others are, at accordance with the instant invention, N through S, inbest, yellow and, at the worst, black (A). The synergistic clusive, remain white longer and, in fact, two Q and R, efiect is thus demonstrated. remain white even to the end of the 150 minute heating period. EXAMPLE II EXAMPLE Plastisol-type resin compositions are made with the Th fonowmg formulatlons: e procedure of Example I is repeated substituting for the vinyl chloride resin the following halogenated hydrocarbon resins, including copolymers of vinyl chloride:

Composition E F G H v nyl chlor de-v nylacetate copolymer (88:12)

20 20 vinyl chloride-vinylacetate copolymer (96:4) Dibutyl tinbis-2-ethylhexylthiog1yco1ate 0.4 0 0.2 vinyl chloride-Z-ethylhexylacrylate copolymer (80:20) g gi gggi fi gf g 8 5 3 vinyl chloride-vinylidene chloride copolymer (90:10)

vinyl chloride-acrylonitrile copolymer (90:10) The ingredients are mixed together until homogeneous polyqhlorobutadlene and placed in tubes. The tubes are immersed in a bath at chlonnated Polyflhylfine 180 C. and the compositions are observed for color polycllchlmostyrene changes at 15 min. intervals. chlonnated rubber It is found that composition E, the unstabilized resin, It is found that Compositions with better Stability t0 has become d red in 15 minutes; the composition heat and lightare obtained with the mixture of stabilizers stabilized only with the sulfur compound F has turned than are Obtamed Wlth elthef 310116- amber in minutes; the composition stabilized only EXAMPLE V with the maleate G also has become amber in 75 minutes; Plastic compositions of the following type are f but the composition with both stabilizers together H related:

Composition T U V W X Y Z AA B B Polyvinyl chloride 1 100 100 100 100 100 100 100 100 Stabilizer:

Dibutyltin bis-(2-ethylhexyl-thioglycolate) 2.0 1.333 1.0 0.666 0.50 0.40 0.333 0.286 0.0 Dibutyltinmaleate 0.0 0.666 1.0 1.333 1.50 1.60 1.666 1. 714 2,0

rnains colorless even at minutes. Thus the combination The ingredients are mixed together, then compounded of stabilizers provides a composition with better resistance on a plastics mill for 4 minutes at 176-177 C. The hot to heat than is provided by either alone. batches are sheeted off at a thickness of about 0.050 inch EXAMPLE III 35 and samples of the sheeted stocks are heated at 180 C.

. in a circulating air oven. The color of the samples is Plastic compositions with the following formulations observed when they are taken off the mill at 15 or 30 are prepared: minute intervals in the oven:

Composition I J K L M N O P Q R S Polyvinyl chloride 1 1 100 100 100 100 100 100 100 100 Stabilizer:

Dibutyl tin bis-(Z-ethylhexyl thioglycolate) Dibutyl tin bis-lauryl mercaptide Dibutyl tin bis-thiobenzoate Dibutyl tin bis-(mono-2-ethylhexyl maleate. Dibutyl tin maleate The ingredients are mixed with 0.5 part of stearic acid per 100 parts of polyvinyl chloride then milled on a plas- Composmon' Observatlo tics mill for 4 minutes at 171 C. Samples of the sheeted T White off the mill; light brown at min.; stocks are heated at 180 C. in a circulating air oven dark brown at minutes. and observations of the color are made at 30 minute 50 U White fi the n light brown at min; intervals, for a maximum of 150 minutes: dark brown at minutes C i i Observation V White ofi the mill; light brown at 180 min;

I White initially; yellow within 30 minutes; dark ow at 210 mlnutes.

remains yellow. 55 W White off the mill; light brown at min.; I Amber during 120 min.; becomes black bedark brown at 225 minutes.

fore end of 150 min. X K Becomes yellow within 30 min.; remains Y DQ ellow throughout. L Wiiite initially; becomes yellow at 60 min.; 60 Z f" g g P at 195 becomes amber at 120 min. ar rown a mum M White initially; becomes yellow at 60 min.; AA

is amber at 150 min. BB White off the mill; blackening at 135 min.; N White initially; becomes yellow at 90 min; black at 165 minute remains yellow throughout. 65 White initlauy; becomes yellow at 120 Thus, it is found that compositions V, W, X and Y which contain the mixed stabilizers in sulfur-maleate ratios of Q Remams White for entire 150 1 to 1; 1 to 2; 1 to 3; and 1 to 4, respectively, are R 9. markedly superior to compositions T, U, Z, AA and BB, Whlte mmany; becomes yellow at 120 70 which contain equal amounts of the organo-tin sulfur Thus it is found that those compositions containing both stabilizer alone; the mixed stabilizers at sulfur-maleate sulfur-containing organo-tin and organo-tin maleate staratios of l to 0.5, 1 to 5, 1 to 6 and the maleate stabilizer bilizers exhibit better heat stability than those containing alone. The synergistic effect resides in compositions V,

equal amounts of only the individual types, I, J and K, W, X and Y in which for each part of sulfur-stabilizer and L and M, respectively. The compositions stabilized in 75 there is present from 1 to 4 parts by weight of the maleate.

Compositions with stability to heat and light enhanced over that obtainable with equal amounts of either stabilizer alone are obtained by adding to polyvinyl chloride from about 0.5 to 10 parts by weight of mixtures of the following stabilizers, I and II, the mixture containing for each part of the sulfur stabilizer (I) from 1 to 4 parts 7 EXAMPLE v1 We claim: 1. A stabilizing mixture consisting essentially of dibutyltin bis-(Z-ethylhexyl thioglycolate) and from about 1 to 4 parts by weight of dibutyltin maleate for each part by weight of said thioglycolate.

2. A polyvinyl chloride resin stabilized against heat and light with about 2% by weight, based on the weight of polyvinyl chloride present, of the stabilizing mixture DONALD E. CZAJA, Primary Examiner V. P. HOKE, Assistant Examiner US. Cl. XiR. 

